Compositions comprising a mixture of sulfur-vulcanizable ethylene/propylene/dicyclopentadiene copolymers with sulfur vulcanizable ethylene/propylene/butadiene copolymers

ABSTRACT

There are disclosed new unsaturated sulfur-vulcanizable compositions comprising mixtures of at least one unsaturated, substantially amorphous, sulfur-vulcanizable copolymer of ethylene, propylene, and dicyclopentadiene with at least one unsaturated, substantially amorphous, sulfur-vulcanizable copolymer of ethylene, propylene and butadiene. The compositions are unsaturated and vulcanizable to elastomers having excellent mechanical and dynamic properties by means of sulfur-containing recipes, at vulcanization rates appreciably higher than can be obtained with the sulfur-vulcanizable copolymers of ethylene, propylene and dicyclopentadiene alone.

United States Patent [151 3,670,055 Cameli et al. [4 1 June 13, 1972 [54] COMPOSITIONS COMPRISING A [56] References Cited MIXTURE 0F SULFUR-VULCANIZABLE ETHYLENE/PROPYLENE/DICYCLOPEN U1 STATES PATENTS TADIENE COPOLYMERS WITH 3,000,866 9/1961 Tamey ..260/80.5 SULFUR VULCA ZAB FOREIGN PATENTS OR APPLICATIONS ETHYLENEIPROPYLENE/BUTADIENE 978,874 12/1964 Great Britain ..260/80.7

COPOLYMERS Inventors: Nazzareno Cameli; Paolo Longi; Alberto Valvassori; Umberto l lisi, all of Milan,

Italy Assignee: The B. F. Goodrich Company, Akron,

Ohio

Filed: April 1, 1970 Appl. No.: 24,865

Foreign Application Priority Data April 2, 1969 Italy ..l4983 N69 US. Cl. ..260/889, 260/235 A, 260/23.7 M,

260/4l.5 R, 260/795 B Int. Cl ..C08l' 29/12, C08d 9/08 Field of Search ..260/889, 80.78, 80.7

Primary Examiner-Samuel l-l. Blech Assistant Examiner-C. Secairo Attorney-Ernest K. Bean and J. Hughes Powell, Jr.

[5 7] ABSTRACT 5 Claims, No Drawings COMPOSITIONS COMPRISING A MIXTURE OF SULFUR- VULCANIZABLE ETI-IYLENE/PROPYLENE/DICYCLOPENTADIENE COPOLYMERS WITH SULFUR VULCANIZABLE ETI-IYLENE/PROPYLENE/BUTADIENE COPOLYMERS PRIOR ART Sulfur-vulcanizable, unsaturated, substantially amorphous co-polymers of ethylene, propylene and dicyclopentadiene are disclosed in Italian patent No. 649,768.

Sulfur-vulcanizable, unsaturated, substantially amorphous copolymers of ethylene, propylene and butadiene are disclosed in Italian Pat. Nos. 566,913; 664,768 and 664,770.

As disclosed in the patents mentioned the copolymers described therein are obtained with the aid of catalysts prepared, preferably, from vanadium compounds and organometallic compounds of aluminum, in the presence or absence of hydrocarbon diluents.

The ethylene/propylene/dicyclopentadiene copolymers have the disadvantage that sulfur-vulcanization thereof by conventional methods occurs at a rate whichis not sufficiently high for a practical, commercial process of converting the copolymers to useful elastomers or elastic rubbers. The ethylene/propylene/dicyclopentadiene copolymers require twice the usual vulcanization time and, in the course of time, undergo marked, undesirable variations in their mechanical and dynamic properties owing to the slowness at which the vulcanization reactions proceed.

THE PRESENT INVENTION One object of this invention was to provide new unsaturated compositions comprising the unsaturated, substantially amorphous, sulfur-vulcanizable copolymers of ethylene, propylene and dicyclopentadiene but having markedly increased sulfur-vuleanization rates.

This and other objects are achieved by the present invention in accordance with which we have found that, surprisingly, the drawback of unduly low vulcanization rate possessed by the unsaturated ethylene, propylene, dicyclopentadiene copolymers can be eliminated by mechanically mixing those copolymers with selected quantities of the unsaturated sulfurvulcanizable ethylene, propylene, butadiene copolymers mentioned above.

More particularly, it has been found that the mechanical mixtures of the invention, when sulfur-vulcanized by conventional methods, show very high vulcanization rates substantially equal to, for instance, the sulfur-vulcanization rate of ethylene/propylene/butadiene-1,3 copolymers, or of ethylene/propylene/ethylidene-norbomene copolymers.

The copolymers mixed to obtain the present unsaturated, vulcanizable compositions contain, by mols, from 50 to 80 percent of polymerized ethylene units, from 19 to 50 percent of polymerized propylene units, and from 0.1 to 20 percent of polymerized units of the diene, dicyclopentadiene in the case of one of the copolymers of the mixture, and butadiene in the case of the other.

The mixtures can be prepared in any suitable way, such as, for instance, by dissolving the two copolymers to be mixed in a solvent and then precipitating the mixed copolymers thus obtained in a coagulating medium, or by mixing the two copolymers in a calander, in the absence of solvents.

The copolymer mixtures of this invention which have the highest vulcanization rates are obtained when the molar ratio of polymerized butadiene units to polymerized dicyclopentadiene units present in the mixture is comprised between 5:1 and 1:5. However, good vulcanization rates are achieved, also, when the molar ratio of polymerized butadiene units to polymerized dicyclopentadiene units is comprised between 1:10 and :1.

By reason of their high vulcanization rates, and the excellent mechanical and dynamic properties of the vulcanized products, which are elastomers or synthetic rubbers, the compositions of the invention have considerable practical value.

EXAMPLE 1 In a roller mixer were admixed in a weight ratio of 1:1, two copolymers having the following characteristics:

copolymer A(ethylene-propylene-dlcyclop entadiene): content in propylene 45 by weight content in dicyclopentadiene 4 by weight mooney viscosity 145 copolymer B(ethylene-propylene-butadiene): content in propylene content in butadiene mooney viscosity 41% by weight 2.5% by weight 98 One hundred parts by weight of this mixture were then admixed to parts of carbon black ISAF, 55 parts of Flexon 766 oil, 1 part of stearic acid, 5 parts of zinc oxide, 0.75 parts of mercaptobenzothiazol, 1.5 parts of tetramethylthiurammonosulphide and 1.75 parts of sulphur. The mix was then vulcanized in a press at 150 C for different vulcanization times.

The properties of the vulcanized products are recorded in Table I.

The AT index was determined by means of a Goodrich flexometer, according to ASTM 623 standards (25 minutes at 100 C, stroke 4.445 millimeters, 1,800 cycles per min. load on the specimen 10.01 kg/cm; diameter of the specimen 1.78 cm; height of the specimen 2.54 cm).

As appears from the above table, the maximum degree of reticulation (deducible from the values of the elastic modulus) is attained between 60 and 90 minutes of vulcanization.

EXAMPLE 2 The two copolymers A and B, described in example 1, were mixed together in a ratio of 3:1 by weight (A/B 3) and were then vulcanized with the same mix and under the same conditions of Example 1.

The properties of the vulcanized products have been recorded in Table 2.

TABLE II Time in minutes 15 30 60 90 Tensile strength (in Kg/cm) 206 236 236 238 247 228 Elongation at break (in 860 720 600 540 540 510 Elastic modulus at 200% (in Kg/cm) 19 27 34 48 45 51 Elastic modulus at 300% (in Kg/cm) 36 58 79 102 98 98 Permanent set (in 48 32 2O 18 20 16 Goodrich A T (in C) 26 As appears from the recorded data, the vulcanization rate is similar to that of mixture A/B l of example 1.

EXAMPLE 3 Table 3 and 4 record the progressive vulcanization rates of, respectively, copolymer A and copolymer B used for the mixes described in Examples 1 and 2.

TABLE In Time in minutes 60 90 120 180 Tensile strength( in Kglcm 159 248 237 240 237 235 Elongation at break (in 1000 700 600 540 480 480 Elastic modulus at 200% (in Kg/cm) 13 27 37 45 52 55 Elastic modulus at 300% (in Kg/cm) 22 51 78 91 109 114 Permanent set (in 66 30 22 14 12 12 TABLE IV Time in minutes 15 30 6O 90 120 180 Tensile strength (in Kglcm 171 198 211 210 l98 190 Elongation at break (in 760 700 660 660 620 630 Elastic modulus at 200% (in Kg/cm") 2l 27 32 35 31 3O Elastic modulus at 300% (in Kg/cm) 43 56 64 70 62 58 Permanent set (in 48 38 38 32 32 Goodrich A T, in C 40 From the data given in Table lll, it is evident that the vulcanization rate of the terpolymer A (ethylene/propylene/dicy clopentadiene) is lower that that of the mixtures A+B reported in Tables I and II.

As a matter of fact, the table shows that the values of the elastic modulus at 300 percent continue to grow with time and that after 60 minutes the value of the modulus is only 68 percent of the value measured after 180 minutes.

From the data reported in Table IV, it is apparent that the properties of vulcanized products obtained from the terpolymer B (ethylene/propylene/butadiene) are inferior to those of the mixtures of the terpolymers A and B described in examples 1 and 2.

More than one copolymer of ethylene, propylene and dicyclopentadiene having a composition in the ranges stated, may be mixed with more than one copolymer of ethylene, propylene and butadiene having a composition in the range stated, in preparing the present vulcanizable compositions.

The compositions can be converted to manufactured shaped articles of any kind, by known methods simultaneously with, or prior to, vulcanization thereof, to obtained shaped, elastomeric articles having a wide variety of practical uses.

As will be apparent, changes and modifications in details may be made in practicing the invention without departing from the spirit thereof. Therefore, we intend to include in the scope of the appended claims all such modifications as will be obvious to those skilled in the art from the description and working examples given herein.

We claim:

1. Sulfur-vulcanizable unsaturated polymeric compositions comprising (A) a copolymer containing from 50 to percent polymerized ethylene units, from 19 to 50 percent polymerized propylene units and from 0.1 to 20 percent dicyclopentadiene units and (B) a copolymer containing from 50 to 80 percent of polymerized ethylene units, 15 to 19 percent polymerized propylene units and from 0.1 to 20 percent of polymerized butadiene units, containing amounts of (A) and (B) to provide a molar ratio of butadiene units to dicyclopentadiene units between 1:10 and 10:1.

2. A composition of claim 1 wherein the molar ratio of butadiene units to dicyclopentadiene units is between 1.525. 1.

3. A composition of claim 1 containing as a vulcanizing agent sulfur or sulfur donors.

4. A composition of claim 1 in a vulcanized state. 5. A composition of claim 1 wherein the ratio of (A) to (B) is from about 1:1 to about 3:1. 

2. A composition of claim 1 wherein the molar ratio of butadiene units to dicyclopentadiene units is between 1.5:5.1.
 3. A composition of claim 1 containing as a vulcanizing agent sulfur or sulfur donors.
 4. A composition of claim 1 in a vulcanized state.
 5. A composition of claim 1 wherein the ratio of (A) to (B) is from about 1:1 to about 3:1. 